I have a couple chest freezers. I was wondering if anybody uses that rigid insulation inside their freezer? Either for the top or the side walls. Were my freezers are, especially in the summer it gets really hot. I thought this might help with the compressor from working so hard.

I made the lid on my keezer out if 5/4" 1x8s. Inside the collar I fitted rigid foam. Works well but it only has to contend with basement temps. I would think that lining the entire inside of a chest freezer with rigid foam would work like putting a sweater on a radiator. The cold seeps in through the walls.

Are you talking about the collar or the whole freezer? Most people add insulation to their collars, but as remthewanderer said you can't insulate the inside walls since that's where the cold comes from.

Putting the rigid foam insulation on the collar is what most people do. I use the 2 inch myself. You wouldnt want to line the inside walls as that is where the cold comes from. The lid would be insulatable if that is your goal. Though usually they are insulated reasonably well already.